Since the 1930""s, the primers for small arms ammunition have, generally, contained Lead Styphnate as a primary explosive, Tetracene to sensitize the Lead Styphnate, Barium Nitrate for an oxidizer, Antimony Sulfide for a frictionator and fuel, a secondary explosive like PETN for brisance, and various gums as a binder. These primers were very successful for many years and are still in use today. They are very reliable, moisture resistant, and stable in storage and use. They were a great improvement over the corrosive Potassium Chlorate and Mercury Fulminate primer mix formulations in use prior to that time.
Now, however, there has been a growing demand for a primer that is non-toxic to the shooter and the environment, when fired in indoor ranges. Heavy metal byproducts of primer combustion, such as Lead, Barium, and Antinomy can be harmful when inhaled or ingested by the shooter. Many indoor shooting ranges have been closed in recent years because of these hazards. Consequently, customers are demanding primers that are free of Lead, Barium, and Antimony compounds.
Many patents have been issued over the last few years for priming compositions that are free of these heavy metals. They usually contain Potassium Dinitrobenzofuroxan (KDNBF) or Diazodinitrophenol (DDNP) as a primary explosive, Tetracene as a sensitizer, powdered Aluminum for a fuel, Calcium Silicide, powdered glass, or Boron as a frictionator, and various gums for a binder. The oxidizers used are KNO3, SnO2, CaCO3, MnO2, Sr(NO3)2, etc. Processed propellant material, such as WC 669, and ground double base propellants have been used as a flame enhancers in these priming mixes. These nitrocellulose-based products work as intended, but are not ideal because they are usually granular materials of random size or propellant by-products with graphite, flash suppressants, and other chemicals, which are not desirable in primers.
Another drawback of the Nitrocellulose and processed propellant flame enhancers used previously is that they can result in Nitrocellulose agglomerations or propellant particles of a size that can cause misfires in the ammunition. Further, the Nitrocellulose agglomerations are not easily dispersed and do not blend uniformly throughout the primer mixture. It is known that such masses of these materials have been deposited between the anvil tip and primer cup in Centerfire percussion primers that created a xe2x80x9cdead spotxe2x80x9d which caused the primer to fail to fire on impact of the firing pin. Similar xe2x80x9cdead spotsxe2x80x9d have also been found in Rimfire ammunition when such particles or agglomerations were found to be deposited in the annulus of the cartridge rim.